The Structure of Eukaryotic Cells and the Importance of Membranes
By: Rayonica L. Thomas
South University Online
The Eukaryotic cell has many organelles that have different functions but are all important to the survival of the cell. The cell wall of the cell controls what goes in and out of the cell. One organelle is the Nucleus. The nucleus generally contains the genetic material for the cell. Because it contains the DNA and chromosomes, which affect the proteins that determine the activities of the cell, the nucleus can be considered to be the cell's control center. The nucleus is the most important part of the cell. Another organelle is the nucleolus. The Nucleolus is a dense region in most nuclei in the nucleolus is where the assembly of ribosomes begins. It’s also non membrane bound which means it has no membrane surrounding it. Ribosomes are where protein synthesis takes place. Some are attached to the rough endoplasmic reticulum, but some are free in the cytoplasm.
The endoplasmic reticulum is a series of interconnecting flattened tubular tunnels. There are two sorts of endoplasmic reticulum - rough ER and smooth ER. The rough ER has lots of attached ribosomes. The smooth ER has no attached ribosomes and so looks 'smooth'. The rough ER takes in the proteins made on the ribosomes so that they cannot escape into the cytoplasm. The smooth ER is not involved in protein synthesis, but has other functions.
The Golgi apparatus is composed of small membranous sacs, and is associated with the endoplasmic reticulum (ER). Though its function is still not entirely understood, it seems that proteins from the ER travel to the Golgi apparatus, where they are transformed and packaged into sacs before being moved to their final destination.
Lysosomes are membrane-bound sacs of enzymes. Old and unneeded parts of the cell are broken down by lysosomes and made into small organic molecules that are reused by the cell. Centrioles are organelles...